Videonystagmography

Videonystagmography is a diagnostic method of ear, nose, and throat medicine used for differential diagnosis of vestibular disorders by recording eye movements. The sensorimotor system (sensory perception and movement) is responsible for an intact sense of balance, the central component of which is the vestibulo-ocular reflex (VOR). By transmitting information from the labyrinth via the vestibular nerve (balance nerve) to core areas in the brainstem and ultimately to the eye muscles, the reflex enables postural regulation, gaze stabilization and orientation in space. Dysfunction of the system can lead to dizziness (vertigo) and impairment of the sense of balance. In the patient, this manifests itself, for example, as ataxia (disturbance of movement coordination), vegetative symptoms (nausea/nausea) or disturbance of gaze stabilization, which can be objectively perceived as nystagmus (eye tremor) and registered with the aid of videonystagmography. Depending on the direction or type of nystagmus, one obtains clues to the cause or localization of the damage to the vestibular apparatus.

Indications (areas of application)

The indication for nystagmography is vertigo (dizziness) or disturbance of balance. This is a symptom that, from a differential diagnostic point of view, can underlie a variety of diseases. A recording of nystagmus can provide information about the causes of vertigo. A. Peripheral vestibular dysfunction (balance disorders):

  1. Acute unilateral vestibular loss.
    • Sudden unilateral disturbance of the sense of balance, often after flu-like infections.
    • Sudden violent spinning dizziness that persists for several days. Nausea (nausea) and vomiting.
    • Horizontal/rotatory spontaneous nystagmus, aggravated under suspension of fixation. Affected labyrinth is hyperexcitable/inexcitable in thermal labyrinth testing.
  2. Benign paroxysmal positional vertigo (BPLS).
    • Disturbance of the organ of equilibrium due to floating particles in the endolymph (inner ear fluid).
    • Violent, recurrent (reoccurring) attacks of spinning vertigo, usually caused by certain bearings.
    • Rotatory nystagmus to one side after assuming the head hanging position and nystagmus in the opposite direction when the head is raised again (positioning test, Hallpike maneuver).
  3. Meniere’s disease
  4. Bilateral peripheral vestibular loss.
    • Balance complaints due to bilateral vestibular organ failure. Usually systemic causes such as ototoxic (ear poisoning) drugs or industrial noxious agents (environmental/workplace exposures). Locally also possible due to labyrinthitis (inflammation of the labyrinth) or congenital (congenital) malformations.
    • No nystagmus detectable because there is no predominance of one side. On thermal labyrinth testing, nystagmus is very mild.

B- Central/neural vestibular dysfunction:

  1. Ischemias (circulatory disturbances) in the brainstem (e.g., cerebellar infarction).
  2. Inflammation (e.g., multiple sclerosis).
  3. Infections (e.g., viral encephalitis).
  4. Tumors (e.g., cerebellopontine angle tumors, gliomas, etc.).
  5. Metabolic disorders (e.g., Wernicke-Korsakow syndrome).
  6. Trauma (eg, brainstem contusion).

Central disturbances of the sense of balance result in characteristic nystagmus:

  • Gaze direction nystagmus (regular gaze direction nystagmus: occurs when looking in a specific direction (not when looking straight ahead) or gaze direction nystagmus irregular: when looking straight ahead and changing the direction of gaze, the nystagmus changes its intensity).
  • Purely rotatory or purely vertical nystagmus.
  • No inhibition of nystagmus by optical fixation
  • Optokinetic reflex disturbed or absent

Contraindications

There are no contraindications to videonystagmography alone.However, individual contraindications should be considered when selecting different forms of nystagmus provocation:

Thermal labyrinth testing must exclude tympanic membrane perforation. If perforation is known, warm/cold air stimulation can be performed as an alternative.

The procedure

Under obscuration (removal of optical fixation), an infrared camera can automatically track pupil movements to record spontaneous or induced nystagmus. The results are automatically analyzed by a computer, with, for example, the speed of the slow nystagmus phase contributing to the analysis.

The examination technique

A video mask with an integrated camera is placed on the patient. In addition, the mask can be darkened to prevent visual fixation. Nystagmus can subsequently be induced in a variety of ways, and the following examination steps are usually performed:

  1. Registration of a spontaneous nystagmus: A test is performed to determine whether a nystagmus is present without head or body movements. Testing is performed with and without gaze fixation and in various eye positions.
  2. Gaze-following test: The patient arbitrarily follows a slow movement, paying attention to the presence of saccades (jerky catch-up movements).
  3. Optokinetic stimulation: when the head is held firmly, a striped pattern that fills as much of the field of view as possible is moved to the left and right. Optokinetic nystagmus is physiological and should be present in healthy individuals.
  4. Rotatory stimulation: by means of a rotating chair, a rotatory nystagmus is induced, which is also physiological and provides information about the correct function of the vestibuloocular reflex (VOR), for example.
  5. Thermal irritation: rinsing the external auditory canal with cold and warm water irritates the labyrinths individually, so it must be physiological to induce nystagmus.
  6. Position and attitude test: nystagmus can be provoked by adopting different head or body positions. In static position testing, the patient is slowly placed in a supine, right, left, and body hanging position and tested for nystagmus. The assumed position itself is the trigger of the eye movement. The dynamic positioning test (according to Hallpike-Dix), on the other hand, is a method in which a nystagmus is triggered by a change in position. The patient is thereby quickly moved from a sitting position to a head hanging position and back to sitting again, so that the movement may cause a positional nystagmus.

Possible complications

No complications are expected with videonystagmography alone. However, due to the different types of nystagmus induction, reactions other than eye movements may occur:

  • Nausea (nausea) and vomiting (vegetative symptoms especially during rotatory and thermal stimulation).
  • Increased dizziness
  • Brief disorientation/dizziness